1. Field of the Invention
The present invention relates to a method and an evaluation system, e.g., for a driver assistance system of a motor vehicle, for object detection using a radar sensor.
2. Description of Related Art
An evaluation method for object detection, or rather an object detection system, may be applied, for example, within the scope of an adaptive cruise control and/or vehicle-to-vehicle ranging, or a driver assistance system of a motor vehicle. Such a control system is able to regulate a previously set travel speed and/or a previously set distance from a preceding vehicle or from objects located in the travel direction, or from target objects. This takes place while appropriately taking into account the surroundings of the motor vehicle and additional parameters, if necessary, such as the current weather conditions and visual conditions. Such a regulating system is also designated as adaptive speed regulation or an ACC (adaptive cruise control) system. In the publication of Robert Bosch GmbH, “Adaptive Fahrgeschwindigkeitsregelung ACC, Gelbe Reihe, Ausgabe 2002, Technische Unterrichtung” (“Adaptive Speed Regulation ACC, Yellow Series, 2002 Edition, Technical Instruction”) such adaptive speed regulating devices are described. Particularly in view of the increasing traffic density of current times, the ACC system has to be flexible enough to react suitably to all traffic situations. This, in turn, requires an appropriate object detection sensor system, in order to supply in each travel situation the measured data required for the regulation, with respect to detected target objects or obstacles.
A method for collision avoidance may also be implemented within the scope of a driver assistance system for a motor vehicle, in which, in the case of at least one obstacle approaching during travel, a driving maneuver is carried out or proposed autonomously or semiautonomously. The at least one obstacle is also recorded using an evaluation system for object detection or rather an object detection system.
Such object detection systems or distance sensors are frequently implemented using radar sensors. Published German patent document DE 195 30 065 proposes a monostatic FMCW radar sensor for a vehicle for detecting objects, in which at least one antenna feed, in conjunction with a dielectric lens, is developed both for transmitting and for receiving a corresponding echo signal. A plurality of send/receive antennas are focused via a common lens. The FMCW radar sensor described has three side-by-side radiation lobes, which are partially able to intersect and which represent an active area in which an object is able to be detected. Consequently, when this is used in a motor vehicle, a plurality of objects may also be detected simultaneously. It may be distinguished, in this context, whether the objects are traveling in the travel direction of the motor vehicle, are standing at the side of the roadway or are approaching from the opposite direction.
It is desirable to make these radar sensors as small as possible in their dimensions, particularly in view of the space they require and the place of installation for them, that is to be selected. The relatively low aperture conditioned by this, particularly of the beam-forming optical elements or of the radar sensors, results in a low angular separation resolution capability, based on the respective radar beam lobes or beams that are relatively broad with respect to the angular range. Beams are usual that have 6 dB widths and an angular range of clearly more than 5°. Using known evaluation methods for object detection, target objects, for instance, which are at a distance of 2° from each other are not able to be separated. However, this could perhaps be important in the case of a so-called lane situation, especially on a multilane expressway or the like, if one's own vehicle is located in the middle lane and if there are also vehicles in the right lane and the left lane ahead of one's own vehicle in the travel direction. Depending on the distance from the other vehicles, it may happen, now, that the individual radar beam lobes cover several vehicles and that it therefore can no longer be ascertained whether the detected target objects are located in the right or the left lane, or whether an additional target object is located in the middle lane, that is, the lane traveled by one's own vehicle, since the target objects melt down to one target, and are no longer able to be separated into individual measurements, with respect to the angle.
Additional information regarding object detection systems, especially for a motor vehicle, is disclosed in published German patent document DE 199 34 670.